Search results for "Reliability and Quality"
showing 10 items of 386 documents
Benchmark study of undrained triaxial testing of Opalinus Clay shale: Results and implications for robust testing
2021
Triaxial testing of argillaceous rocks and shales is significantly more challenging than conventional rock mechanical testing. The challenges are mainly related to the very low permeability of these geomaterials, and their sensitivity to exposure of atmosphere and brines, which induces variations of water content, suction and effective stress. There are currently no international standards to guide service laboratories for robust testing procedures for shales. A benchmark study of undrained triaxial testing was therefore initiated with three leading service laboratories in shale testing, performing 13 tests and using two different methods of establishing sample saturation prior to deformati…
Impact of humic acids on EYL liposome membranes: ESR method
2015
Abstract In this paper, the effects of model (commercial) and natural (extracted from peat) humic substances on the membrane of liposomes formed with egg yolk lecithin (EYL) are presented. In our research, mass concentrations of fulvic and humic acids were used, which in relation to lecithin varied from 0% to 13%. To study membrane fluidity, electron spin resonance (EPR) was used with two spin probes, penetrating various regions of the lipid bilayer. The effects of model and natural humic substances (humic acids – HAs and fulvic acids – FAs) on the lipid membrane in different regions were researched: the lipid-water interphase, and in the middle of the lipid bilayer. It was shown that FA an…
Memory‐type control charts for censored reliability data
2023
Control charts are commonly used to monitor a process to detect undesirable changes. The main goal of this work is to propose exponentially weighted moving average (EWMA) and cumulative sum (CUSUM) control charts to track a process by utilizing type-I censored generalized exponential (GE) distributed data. In particular, the censored data are replaced with the conditional expected value (CEV). A comparison between CUSUM and CUSUM ignoring unobserved covariates (CUSUM-IUC) charts is also a part of this study. The GE distribution is considered due to its application in reliability analysis. The performance of the charts is evaluated by using the average run length along with the standard devi…
Preliminary magnetic resonance relaxometric analysis of Fricke gel dosimeters produced with polyvinyl alcohol and glutaraldehyde
2017
This work describes the preliminary analysis of Fricke gels dosimeters characterized by a new formulation making use of a matrix of polyvinyl alcohol cross-linked by adding glutaraldehyde and analyzed by means of nuclear magnetic resonance relaxometry. In previous optical studies, these gels have shown promising dosimetric features in terms of photon sensitivity and low diffusion of ferric ions produced after irradiation. In this work, we used a portable nuclear magnetic resonance relaxometer to measure the relaxation times (which are important for dosimetric applications) of these gel materials. For this purpose, we performed a study for optimizing the acquisition parameters with a nuclear…
Metrological performances of voltage and current instrument transformers in harmonics measurements
2018
In the new electrical system scenario, the increasing presence of non-linear loads and renewable energy sources makes the measurement of harmonics an essential task. The accuracy of harmonic measurement firstly depends on the used instrument transformers for voltage and current sensing. Since the behavior of instrument transformers in non-sinusoidal conditions is not always well defined, this paper presents an experimental study on the metrological performances of current and voltage instrument transformers (CTs and VTs) in the presence of harmonics. Proper tests procedures are defined and measurement setups are developed for both CTs and VTs calibration. The analysis is carried out by usin…
Distribution and generation of traps in SiO2/Al2O3 gate stacks
2007
In this work we combine charge-pumping measurements with positive constant voltage stress to investigate trap generation in SiO2/ Al2O3 n-MOSFET. Trap density has been scanned either in energy or in position based on charge-pumping (CP) measurements performed under different operating conditions in terms of amplitude and frequency of the gate pulse. Our results have revealed that the traps are meanly localized shallow in energy level, deeper in spatial position and they are mostly generated near the Si/SiO2 interface. (C) 2007 Elsevier Ltd. All rights reserved.
On the relationship between occlusion times and in-car glance durations in simulated driving
2023
Drivers have spare visual capacity in driving, and often this capacity is used for engaging in secondary in-car tasks. Previous research has suggested that the spare visual capacity could be estimated with the occlusion method. However, the relationship between drivers’ occlusion times and in-car glance duration preferences has not been sufficiently investigated for granting occlusion times the role of an estimate of spare visual capacity. We conducted a driving simulator experiment (N = 30) and investigated if there is an association between drivers’ occlusion times and in-car glance durations in a given driving scenario. Furthermore, we explored which factors and variables could explain t…
Evaluating Safety Systems for Machine Tools with Computer Numerical Control using Analytic Hierarchy Process
2019
Computer numerical control (CNC) machine tools are complex production systems with fully automatic machine parts. Nowadays, high feed rates and machining speeds are used during the machining process. Human operators are still needed to set-up the machine, load/unload workpieces and parts, load the machining code, and supervise the machining process. The operators work in an environment where automated high-speed motions occur, and consequently, CNC machine tools have to be equipped with safety systems. The approach presented in this paper was to evaluate the main safety systems of CNC machine tools based upon the analytic hierarchy process (AHP). The analyzed systems were divided into six m…
Molecular dynamics simulations of heavy ion induced defects in SiC Schottky diodes
2018
Heavy ion irradiation increases the leakage current in reverse-biased SiC Schottky diodes. This letter demonstrates, via molecular dynamics simulations, that a combination of bias and ion-deposited energy is required to produce the degradation. Peer reviewed
Understanding risky behaviours in nuclear facilities: The impact of role stressors
2018
Abstract Risky behaviours have received little attention in the safety literature in recent years, compared to safety behaviours such as safety compliance or safety participation. However, it is important to focus on risky behaviours and their predictors in order to prevent accidents. The aim of this study is to explore the impact of role stressors (role ambiguity and role overload) on risky behaviours, and the mediating role of dissatisfaction (both job and safety dissatisfaction). The sample consists of 566 employees from two nuclear power plants in Spain. Structural equation modelling is used to determine the effects of role ambiguity and role overload on risky behaviours. Role stressors…